Chapter 7 · Health
Practice: read the chart
Compute a change from two numbers
Percentage change = (new minus old) divided by old, times 100. Use the cited values; hints are optional.
Toolbox
- Formula: Change in per cent = (new - old) / old x 100.
- Values: Road deaths: 3,026 in 2016, 1,660 in 2025. PM10 days at Bujaka: 78 in 2016, 23 in 2024.
Hints, feedback and the worked solution need JavaScript. The tasks are listed below.
Challenge 1 Level 1: Guided
Road deaths fell from 3,026 in 2016 to 1,660 in 2025. By about what per cent?
First find how many fewer people died.3,026 minus 1,660 is the fall. Divide it by the old value, 3,026.1,366 divided by 3,026 is about 0.45.(1,660 - 3,026) / 3,026 = -1,366 / 3,026 = -0.451, a fall of 45.1%.Challenge 2 Level 2: Supported
PM10 days over the limit at the Bujaka station fell from 78 in 2016 to 23 in 2024. By about what per cent?
Use the same formula; the old value is 78.(23 - 78) / 78 = -55 / 78 = -0.705, a fall of 70.5%.Challenge 3 Level 3: Independent
A friend says: 'Life expectancy of men rose 8.7 years, so a man born today will live 8.7 years longer than in 1990.' Write down in one sentence what is wrong with that.
Life expectancy at birth is a period measure of mortality in one year (2024), not a forecast for a person. It says that if the mortality rates of 2024 stayed unchanged, a boy born then would live 74.93 years on average.